docs(loudness): document loudness range
docs(loudness): document loudness range

Loudness has been incorrectly documented as having a range of 0-1 per band and 24 in total. In fact,
loudness is not normalised. I replaced the range section with a description of how to approach
consuming the loudness data in different use cases.

fix #288

meyda/meyda,meyda/meyda,hughrawlinson/meyda,meyda/meyda